If one defines personhood on
the basis of those who consciously performing personal acts, those who are
asleep would be classified as non-persons and could be killed during a
nap. If one defines personhood on the basis of those who have a present
capacity to perform personal acts, those who are in a coma could be killed
at any point during their coma.

http://www.godandscience.org/abortion/sld036.html
Last Modified June 14, 2008